Scanning apparatuses are widely used for scanning images of documents. The scanned images can be converted into electronic files, which are then stored, processed or spread. With increasing development of scanning technologies, the scanning apparatuses have experienced great growth and are now rapidly gaining in popularity.
In the early stage, the scanning apparatus can scan one side of the document. For scanning both sides of the document, after one side of the document has been scanned, the document should be manually turned over so as to scan the other side of the document. As known, the process of manually turning over the document is troublesome. Recently, an automatic document feeder is usually integrated into the scanning apparatus. After a stack of documents to be scanned are placed on the sheet input tray of the automatic document feeder, the sheet-feeding mechanism of the automatic document feeder will successively transport the sheet to perform the scanning operation without the need of manually turning over the documents. This means of automatically feeding the sheet sheets is both time-saving and efficient. It is found that the scanning apparatuses are improved according to the generation development and the diverse demands.
Generally, the pick-up roller and the separation roller of the sheet-feeding type scanning apparatus are abraded after a long-term use period. As such, a so-called double feeding problem occurs when a stack of documents are fed into the internal portion of the sheet-feeding type scanning apparatus. Once the double feeding problem occurs, two or more documents are simultaneously fed into the internal portion of the sheet-feeding type scanning apparatus. Since second document is partially or completely superimposed with the first document when the double feeding problem occurs, the second document is incompletely scanned or fails to be scanner. In other words, the double feeding problem is detrimental to the performance of the sheet-feeding type scanning apparatus.
Therefore, there is a need of providing a sheet-feeding type scanning apparatus for solving the double feeding problem.